A vehicle may operate autonomously or semi-autonomously, i.e., without input from a human operator to control some or all driving operations, e.g., some or all of steering, propulsion (e.g., throttle), and braking. Autonomous or semi-autonomous operation may not be suitable and/or desired for all driving situations. The human operator may provide input to switch the vehicle to full or partial manual control. However, the human operator may be or become distracted or drowsy, potentially impairing manual control of the vehicle.